Option variable
assume_posDefault value: false
When assume_pos is true
and the sign of a parameter x cannot be determined from the current context
or other considerations,
sign and asksign (x) return true.
This may forestall some automatically-generated asksign queries,
such as may arise from integrate or other computations.
By default, a parameter is x such that symbolp (x)
or subvarp (x).
The class of expressions considered parameters can be modified to some extent
via the variable assume_pos_pred.
sign and asksign attempt to deduce the sign of expressions
from the sign of operands within the expression.
For example, if a and b are both positive,
then a + b is also positive.
However, there is no way to bypass all asksign queries.
In particular, when the asksign argument is a
difference x - y or a logarithm log(x),
asksign always requests an input from the user,
even when assume_pos is true and assume_pos_pred is
a function which returns true for all arguments.